Ruby

Bump rbs from 3.7.0 to 3.8.1 in /steep #5918

Job	Run time
test (3.1, test)	2m 17s
test (3.2, test)	3m 11s
test (3.3, test)	3m 40s
test (3.4, test)	2m 34s
test (head, test)	3m 31s
test (head, stdlib_test rubocop)	2m 11s
test (3.4, stdlib_test)	2m 13s
test (3.4, test, --enable-frozen-string-literal)	2m 28s
test (3.4, stdlib_test, --enable-frozen-string-literal)	2m 5s
test (3.4, lexer templates compile confirm_lexer confirm_templates)	4m 20s
test (3.4, rubocop validate test_doc build test_generate_stdlib raap)	2m 21s
test (3.4, typecheck_test)	1m 4s
	31m 55s

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